Multiple-input multiple-output (MIMO) wireless communications systems utilize multiple transmit and receive antennas to achieve transmit and receiver diversity, which may allow for more reliable communications and/or improved data throughput. While multiple transmit antennas are available, the preamble or the primary synchronization signal in a MIMO system is typically transmitted to the mobile subscriber by utilizing only one effective transmit antenna at the base station. This is due to the fact that during the initial access the subscriber does not know the number of antennas at the base station. As a result, the transmission diversity as an inherent feature for a plurality of antennas is not utilized during the initial access.
In the developing of IEEE 802.16m standard, a broadcast channel (BCH) needs to be decoded by the mobile subscriber following its primary synchronization with the base station. The BCH may contain system-wide parameters in order to enable the initial access. In addition, the BCH may be transmitted by utilizing a plurality of transmit antennas. Instead of providing pilots for the BCH message, cyclic delay diversity (CDD) scheme may be utilized to transmit delayed copies of a preamble from multiple antennas. To accomplish this, information about the number of transmit antennas utilized by the base station and channel estimates need to be obtained before decoding the BCH message.
Therefore, there is a need in the art for conveying the number of transmit antennas that are utilized at the base station, ideally during primary synchronization with the mobile subscriber.